Measurement of vibrations in two tower-typed assistant personal robot implementations with and without a passive suspension system

This paper presents the vibration pattern measurement of two tower-typed holonomic mobile robot prototypes: one based on a rigid mechanical structure, and the other including a passive suspension system. Specific to the tower-typed mobile robots is that the vibrations that originate in the lower part of the structure are transmitted and amplified to the higher areas of the tower, causing an unpleasant visual effect and mechanical stress. This paper assesses the use of a suspension system aimed at minimizing the generation and propagation of vibrations in the upper part of the tower-typed holonomic robots. The two robots analyzed were equipped with onboard accelerometers to register the acceleration over the X, Y, and Z axes in different locations and at different velocities. In all the experiments, the amplitude of the vibrations showed a typical Gaussian pattern which has been modeled with the value of the standard deviation. The results have shown that the measured vibrations in the head of the mobile robots, including a passive suspension system, were reduced by a factor of 16.This work was partially funded by Indra, the University of Lleida, the RecerCaixa 2013 grant, the Government of Catalonia (Comissionat per a Universitats i Recerca, Departament d’Innovació, Universitats i Empresa), and by the European Social Fund (ECO/1794/2015)

Suboptimal Omnidirectional Wheel Design and Implementation

The optimal design of an omnidirectional wheel is usually focused on the minimization of the gap between the free rollers of the wheel in order to minimize contact discontinuities with the floor in order to minimize the generation of vibrations. However, in practice, a fast, tall, and heavy-weighted mobile robot using optimal omnidirectional wheels may also need a suspension system in order to reduce the presence of vibrations and oscillations in the upper part of the mobile robot. This paper empirically evaluates whether a heavy-weighted omnidirectional mobile robot can take advantage of its passive suspension system in order to also use non-optimal or suboptimal omnidirectional wheels with a non-optimized inner gap. The main comparative advantages of the proposed suboptimal omnidirectional wheel are its low manufacturing cost and the possibility of taking advantage of the gap to operate outdoors. The experimental part of this paper compares the vibrations generated by the motion system of a versatile mobile robot using optimal and suboptimal omnidirectional wheels. The final conclusion is that a suboptimal wheel with a large gap produces comparable on-board vibration patterns while maintaining the traction and increasing the grip on non-perfect planar surfaces.This research was funded by the MCI program, grant number PID2020-118874RB-I00

Locomotion system for ground mobile robots in uneven and unstructured environments

One of the technology domains with the greatest growth rates nowadays is service robots. The extensive use of ground mobile robots in environments that are unstructured or structured for humans is a promising challenge for the coming years, even though Automated Guided Vehicles (AGV) moving on flat and compact grounds are already commercially available and widely utilized to move components and products inside indoor industrial buildings. Agriculture, planetary exploration, military operations, demining, intervention in case of terrorist attacks, surveillance, and reconnaissance in hazardous conditions are important application domains. Due to the fact that it integrates the disciplines of locomotion, vision, cognition, and navigation, the design of a ground mobile robot is extremely interdisciplinary. In terms of mechanics, ground mobile robots, with the exception of those designed for particular surroundings and surfaces (such as slithering or sticky robots), can move on wheels (W), legs (L), tracks (T), or hybrids of these concepts (LW, LT, WT, LWT). In terms of maximum speed, obstacle crossing ability, step/stair climbing ability, slope climbing ability, walking capability on soft terrain, walking capability on uneven terrain, energy efficiency, mechanical complexity, control complexity, and technology readiness, a systematic comparison of these locomotion systems is provided in [1]. Based on the above-mentioned classification, in this thesis, we first introduce a small-scale hybrid locomotion robot for surveillance and inspection, WheTLHLoc, with two tracks, two revolving legs, two active wheels, and two passive omni wheels. The robot can move in several different ways, including using wheels on the flat, compact ground,[1] tracks on soft, yielding terrain, and a combination of tracks, legs, and wheels to navigate obstacles. In particular, static stability and non-slipping characteristics are considered while analyzing the process of climbing steps and stairs. The experimental test on the first prototype has proven the planned climbing maneuver’s efficacy and the WheTLHLoc robot's operational flexibility. Later we present another development of WheTLHLoc and introduce WheTLHLoc 2.0 with newly designed legs, enabling the robot to deal with bigger obstacles. Subsequently, a single-track bio-inspired ground mobile robot's conceptual and embodiment designs are presented. This robot is called SnakeTrack. It is designed for surveillance and inspection activities in unstructured environments with constrained areas. The vertebral column has two end modules and a variable number of vertebrae linked by compliant joints, and the surrounding track is its essential component. Four motors drive the robot: two control the track motion and two regulate the lateral flexion of the vertebral column for steering. The compliant joints enable limited passive torsion and retroflection of the vertebral column, which the robot can use to adapt to uneven terrain and increase traction. Eventually, the new version of SnakeTrack, called 'Porcospino', is introduced with the aim of allowing the robot to move in a wider variety of terrains. The novelty of this thesis lies in the development and presentation of three novel designs of small-scale mobile robots for surveillance and inspection in unstructured environments, and they employ hybrid locomotion systems that allow them to traverse a variety of terrains, including soft, yielding terrain and high obstacles. This thesis contributes to the field of mobile robotics by introducing new design concepts for hybrid locomotion systems that enable robots to navigate challenging environments. The robots presented in this thesis employ modular designs that allow their lengths to be adapted to suit specific tasks, and they are capable of restoring their correct position after falling over, making them highly adaptable and versatile. Furthermore, this thesis presents a detailed analysis of the robots' capabilities, including their step-climbing and motion planning abilities. In this thesis we also discuss possible refinements for the robots' designs to improve their performance and reliability. Overall, this thesis's contributions lie in the design and development of innovative mobile robots that address the challenges of surveillance and inspection in unstructured environments, and the analysis and evaluation of these robots' capabilities. The research presented in this thesis provides a foundation for further work in this field, and it may be of interest to researchers and practitioners in the areas of robotics, automation, and inspection. As a general note, the first robot, WheTLHLoc, is a hybrid locomotion robot capable of combining tracked locomotion on soft terrains, wheeled locomotion on flat and compact grounds, and high obstacle crossing capability. The second robot, SnakeTrack, is a small-size mono-track robot with a modular structure composed of a vertebral column and a single peripherical track revolving around it. The third robot, Porcospino, is an evolution of SnakeTrack and includes flexible spines on the track modules for improved traction on uneven but firm terrains, and refinements of the shape of the track guidance system. This thesis provides detailed descriptions of the design and prototyping of these robots and presents analytical and experimental results to verify their capabilities

Exploration of robotic-wheel technology for enhanced urban mobility and city scale omni-directional personal transportation

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2008.Includes bibliographical references (leaves 50-52).Mobility is traditionally thought of as freedom to access more goods and services. However, in my view, mobility is also largely about personal freedom, i.e., the ability to exceed one's physical limitations, in essence, to become "more than human" in physical capabilities. This thesis explores novel designs for omni-directional motion in a mobility scooter, car and bus with the aim of increasing personal mobility and freedom. What links these designs is the use of split active caster wheel robot technology. In the first section, societal and technological impacts of omni-directional motion in the city are examined. The second section of the thesis presents built and rendered prototypes of these three designs. The third and final section, evaluates implementation issues including robotic controls and an algorithm necessary for real world omni-directional mobility.by Raul-David Valdivia Poblano.S.M

Mobile manipulator robot: omni 3 wheels manipulator robot

Mestrado de dupla diplomação com a Université Libre de TunisRobots are electromechanical machines having ability to perform tasks or actions on some given electronic programming. While Omni directional mobile robots have been popularly used in several applications since they can respond more quickly and it would be capable of more sophistication. A robotic arm is a type of mechanical arm, usually programmable, with similar functions to a human arm; the arm may be the sum total of the mechanism or may be part of a more complex robot. This work proposes to design and create a model of a three-Wheeled Omnidirectional manipulator robot that can move faster and transport materials and placed on a processing machine by combine the two type of robots. Using an electrical, mechanical and power supply model controlled by PID control and serial communication between two microcontrollers.Os robôs são máquinas electromecânicas com capacidade para executar tarefas ou acções em alguma programação electrónica dada. O robôs móveis Omni direccionais têm sido popularmente empregados em várias aplicações porque podem responder mais rapidamente e seriam capazes de ser mais sofisticados. Também um braço robótico é um tipo de braço mecânico, geralmente programável, com funções semelhantes às de um braço humano; o braço pode ser a soma total do mecanismo ou pode fazer parte de um robô mais complexo. Este trabalho propõe-se conceber e criar um modelo de robô manipulador Omnidireccional de três rodas que pode mover-se mais rapidamente e transportar materiais e ser colocado numa máquina de processamento através da fusão dos dois tipos de robôs. Utilizando um modelo eléctrico, mecânico e de alimentação controlado por controlo PID e comunicação em série entre dois microcontroladores

Design and FDM/FFF Implementation of a Compact Omnidirectional Wheel for a Mobile Robot and Assessment of ABS and PLA Printing Materials

This paper proposes the design and 3D printing of a compact omnidirectional wheel optimized to create a small series of three-wheeled omnidirectional mobile robots. The omnidirectional wheel proposed is based on the use of free-rotating passive wheels aligned transversally to the center of the main wheel and with a constant separation gap. This paper compares a three inner-passive wheels design based on mass-produced parts and 3D printed elements. The inner passive wheel that better combines weight, cost, and friction is implemented with a metallic ball bearing fitted inside a 3D printed U-grooved ring that holds a soft toric joint. The proposed design has been implemented using acrylonitrile butadiene styrene (ABS) and tough polylactic acid (PLA) as 3D printing materials in order to empirically compare the deformation of the weakest parts of the mechanical design. The conclusion is that the most critical parts of the omnidirectional wheel are less prone to deformation and show better mechanical properties if they are printed horizontally (with the axes that hold the passive wheels oriented parallel to the build surface), with an infill density of 100% and using tough PLA rather than ABS as a 3D printing material

Design of a Spherical UGV for Space Exploration

The paper presents the design of a spherical UGV (Unmanned Ground Vehicle) for exploration of critical, unknown or extended areas, such as planetary surfaces. Spherical robots are an emerging class of devices whose shape brings many advantages, e.g. omni-directionality, sealed internal environment and protection from overturning. Many dedicated sensors can be safely placed inside the sphere and the robot can roll in any direction without getting stuck in singular configurations. Specifically, the proposed UGV is thought to collect images and environmental data, so required sensors are firstly discussed to evaluate in sequence of the payload in terms of size and energy consumption. The most effective drive mechanism is selected considering several possible concepts and carrying a trade-off process based on the requirements for a space mission. The optimal solution involves the use of a single pendulum: a hanging mass, attached to the central shaft of the sphere, is shifted to produce rolling. The design issues due to the selected mechanism are discussed, showing the effect of design parameters on the expected performance. For instance, the barycenter offset from the center of the sphere plays a crucial role and affects the maximum step or inclines that can be overcomed. Therefore, the pre-design phase is conducted by discussing the functional design of the robot and introducing a differential mechanism for driving and steering. A quasi omni-directionality is achieved and the mechanical components, opportunely designed according to the loads acting on the device, are arranged to match the mission requirements. Moreover, the mechatronic integration is discussed: microcontrollers, drive electronics, sensors and batteries are sized in order to reach 3 hours of continuous operation. The multibody system is finally modelled in Matlab-Simscape to verify the mechanism for the UGV testing in specific cases. Results show that a suitable layout is a 0.5 m diameter spherical UGV with a steel main structure, mounting 2 DC motors that activate a bevel gear by means of pulleys and timing belts. The spherical shell, with the internal mechanism and electronics, has a total mass of 25 kg and from standstill it can climb up to 15 degrees inclines or steps up to 25 mm, as proved by Matlab simulations. Future works will focus on the realization of the physical prototype, as well as navigation and control strategies